WO2024075921A1

WO2024075921A1 - Polyethylene packaging material with excellent printability and easy manufacturing

Info

Publication number: WO2024075921A1
Application number: PCT/KR2023/007383
Authority: WO
Inventors: Joohyun NAM; Eunjung BAEK; Jaemyoung SON; Byoungcheon JO
Original assignee: Sk Innovation Co., Ltd.; Sk Geo Centric Co., Ltd.
Priority date: 2022-10-06
Filing date: 2023-05-30
Publication date: 2024-04-11

Abstract

Provided are a polyethylene film of a multilayer structure which has excellent printability and is easy to manufacture, and a packaging material manufactured therefrom. Specifically, a polyethylene multilayer structure film which is recyclable so that it does not cause environmental pollution and does not have mechanical properties and thermal properties which are not greatly deteriorated as compared with a conventional laminated film of different materials and a packaging material manufactured therefrom, so that it may minimize damage in the process of print processability and commercialization, and a packaging material manufactured therefrom are provided.

Description

POLYETHYLENE PACKAGING MATERIAL WITH EXCELLENT PRINTABILITY AND EASY MANUFACTURING

The present disclosure relates to a polyethylene film of a multilayer structure which has excellent printability and is easy to manufacture, and a packaging material manufactured therefrom.

Packaging materials are manufactured by resin films mainly composed of resin materials. Among them, a resin film composed of polyolefin has moderate flexibility and excellent transparency, and thus, is being widely used in packaging materials.

The packing material used is usually obtained by bonding a resin film composed of polyethylene to a resin film composed of polyester, polyamide, or the like having excellent mechanical properties and thermal properties and the like. That is, a common packaging material is composed of a laminate film in which a base material and a heat sealing layer are made of different kinds of resin material. Thus, since it is difficult to separate different kinds of resin materials in a conventional packaging material, recycling is practically impossible, and thus, it emerges as a major social problem in terms of environment.

In order to solve the problem, studies for developing a technology of implementing a recyclable packaging material, in particular, for manufacturing a packaging material using a resin film formed of only a polyolefin-based single material are in progress. However, as mentioned above, since a packaging material manufactured of a polyolefin resin single material has deteriorated mechanical properties as compared with a conventional packaging material manufactured by laminating different kinds of base materials, the durability of the packaging material composed thereof is also deteriorated, and thus, there is a high possibility of defects in a printing process of the packaging material, and the packaging material is easily damaged in the process of use such as transportation and storage. In addition, since a packaging material manufactured of a single material of polyolefin resin has deteriorated thermal resistance as compared with a resin used as a conventional base material, there is a high possibility of defects in the process of a heat sealing process for forming a packaging material.

Thus, a multilayer structure film in which a polyolefin resin having different mechanical and thermal properties based on differences in density, additives, composition ratios, and the like while using a polyolefin-based single material is laminated is constantly being developed, but it is still difficult to obtain excellent mechanical and thermal properties and it is also not easy to use in terms of cost, and in particular, there is a limitation to implement a packaging material which may be used even at a low temperature, and thus, improvement is being demanded.

For example, Japanese Patent Laid-Open Publication No. 2020-037189 discloses a laminated film for a packaging material having a polyolefin content of 80 parts by weight with respect to the film, but which still has a problem of deteriorated durability at a low temperature, and Japanese Patent Registration No. 6814287 discloses a recyclable laminated film of a polyethylene single material, but it is still difficult to obtain excellent thermal resistance and heat sealability is deteriorated.

Accordingly, development of a new film, which is a resin film formed of only a single material, is easily recyclable, may solve environmental problems, does not have mechanical and thermal properties which are greatly deteriorated as compared with a conventional laminated film of different materials, maintains excellent physical properties in various temperature ranges to be commercialized, and also has excellent printability and processability, and a packaging material, is demanded.

[Related Art Documents]

[Patent Documents]

Japanese Patent Laid-Open Publication No. 2020-037189 (March 12, 2020)

Japanese Patent Registration No. 6814287 (December 22, 2020)

An object of the present disclosure is to provide a polyethylene multilayer structure film which is recyclable so that it does not cause environmental pollution and does not have mechanical properties and thermal properties which are not greatly deteriorated as compared with a conventional laminated film of different materials and a packaging material manufactured therefrom, so that it may minimize damage in the process of print processability and commercialization, and a packaging material manufactured therefrom.

Another object of the present disclosure is to provide a polyethylene multilayer structure film which has excellent transparency and may satisfy printing efficiency to be desired, and a packaging material manufactured therefrom.

Still another object of the present disclosure is to provide a polyethylene multilayer structure film which has excellent heat sealability and high-speed bag making processability, and a packaging material manufactured therefrom.

In one general aspect, a polyethylene multilayer structure film includes: a printed layer (A) and a heat sealing layer (B), wherein the printed layer (A) has a monolayer or multilayer structure including a layer including a mixed resin including any one or more polyethylene resins selected from a linear low-density polyethylene resin (LLDPE), a metallocene linear low-density polyethylene resin (mLLDPE), and a low-density polyethylene resin (LDPE) and a high-density polyethylene resin (HDPE), when the printed layer (A) is a single layer, the high-density polyethylene resin is included at 50 wt% to 95 wt% and when the printed layer (A) is multi-layered, a structure of an outermost layer (A1) and an intermediate layer (A2) is included, in which the outermost layer (A1) includes 50 wt% or more of the high-density polyethylene resin and at least one layer of the intermediate layer (A2) includes 90 wt% or less of the high-density polyethylene resin,

the heat sealing layer (B) includes an upper layer (B1), a middle layer (B2), and an adhesive layer (B3), the upper layer (B1) and the middle layer (B2) include any one or more polyethylene resins selected from a linear low-density polyethylene resin (LLDPE), a metallocene linear low-density polyethylene resin (m-LLDPE), a medium-density polyethylene resin (MDPE), and a high-density polyethylene resin (HDPE), the adhesive layer (B3) includes a polyolefin elastomer and/or a polyolefin plastomer, and a difference in melting temperature between the adhesive layer (B3) of the heat sealing layer (B) and the single layer of the printed layer (A) or the outermost layer (A1) of the printed layer (A) when the printed layer is multi-layered satisfies the following Equation 1:

[Equation 1]

wherein TmA is a melting temperature of the single layer of the printed layer (A) or the outermost layer (A1) of the printed layer (A) when the printed layer is multi-layered, and TmB is a melting temperature of the adhesive layer (B3) of the heat sealing layer (B).

According to an exemplary embodiment of the present disclosure, an MD elongation ratio in accordance with ASTM D 638 between the printed layer (A) and the heat sealing layer (B) may satisfy the following Equation 2, and a TD elongation ratio may satisfy the following Equation 3:

[Equation 2]

[Equation 3]

wherein MA is an MD elongation of the printed layer (A), MB is an MD elongation of the heat sealing layer (B), TA is a TD elongation of the printed layer (A), and TB is a TD elongation of the heat sealing layer (B).

According to an exemplary embodiment of the present disclosure, the printed layer may not be stretched.

According to an exemplary embodiment of the present disclosure, a shrinkage rate of the printed layer (A) may be 30% or less in MD under the conditions of 0.02 N and 128°C and 20% or less in MD under the conditions of 0.05 N and 128°C.

According to an exemplary embodiment of the present disclosure, the high-density polyethylene resin included in the printed layer (A) may have a density of 0.935 to 0.97 g/cm³ and a melt index of 0.2 to 10 g/10 min, and the linear low-density polyethylene resin (LLDPE), the low-density polyethylene resin (LDPE), and the metallocene low-density polyethylene resin (m-LDPE) included in the printed layer (A) may have a density of 0.900 g/cm³ or more and less than 0.935 g/cm³ and a melt index of 0.2 to 20 g/cm³.

According to an exemplary embodiment of the present disclosure, the melting temperature of the single layer of the printed layer (A) or the outermost layer (A1) of the multiple layers of the printed layer (A) may be 127°C or higher, and the melting temperature of the adhesive layer (B3) of the heat sealing layer (B) may be 108°C or lower.

According to an exemplary embodiment of the present disclosure, the printed layer (A) may have a structure of three or more layers, the printed layer (A) may include the outermost layer (A1), the intermediate layer (A2), and a lower layer (A3), and the lower layer (A3) may be a mixed resin of any one or more layers selected from a low-density polyethylene resin (LDPE), a linear low-density polyethylene resin (LLDPE), and a metallocene linear low-density polyethylene resin (m-LLDPE) and a high-density polyethylene resin (HDPE).

According to an exemplary embodiment of the present disclosure, the adhesive layer (B3) of the heat sealing layer (B) may further include any one or more polyethylene resins selected from a low-density polyethylene resin (LDPE), a linear low-density polyethylene resin (LLDPE), a metallocene linear low-density polyethylene resin (m-LLDPE), a medium-density polyethylene resin (MDPE), and a high-density polyethylene resin (HDPE).

According to an exemplary embodiment of the present disclosure, the printed layer (A) may have a haze of 25% or less, and an elastic modulus value in MD and TD of 4,000 kgf/cm² or more, as measured by a 1% secant modulus method.

According to an exemplary embodiment of the present disclosure, a thickness ratio of the upper layer (B1), the middle layer (B2), and the adhesive layer (B3) in the heat sealing layer (B) may be 1:1 to 10:0.2 to 2.

According to an exemplary embodiment of the present disclosure, the printed layer (A) may have a film thickness of 60 μm or less.

According to an exemplary embodiment of the present disclosure, the heat sealing layer (B) may have a film thickness of 30 to 250 μm.

According to an exemplary embodiment of the present disclosure, the polyethylene multilayer structure film may have a total thickness of 300 μm or less.

According to an exemplary embodiment of the present disclosure, the printed layer (A) may be 30 N or more and the heat sealing layer (B) may be 80 N or more in a puncture test in accordance with ASTM D4830.

According to an exemplary embodiment of the present disclosure, the printed layer (A) may have a tensile strength of 400 kgf/cm² or more in MD and 300 kgf/cm² or more in TD, and the heat sealing layer (B) may have a tensile strength of 300 kgf/cm² or more in MD and 300 kgf/cm² or more in TD, in accordance with ASTM D 892.

According to an exemplary embodiment of the present disclosure, the printed layer (A) may have an elongation of 300% or more in MD and 500% or more in TD, and the heat sealing layer (B) may have an elongation of 400% or more in MD and 400% or more in TD, in accordance with ASTM D 638.

According to an exemplary embodiment of the present disclosure, the polyethylene multilayer structure film may be laminated by a dry lamination method.

According to an exemplary embodiment of the present disclosure, one or more blocking layers may be further included between the outermost layer (A1) and the lower layer (A3) of the printed layer (A).

According to an exemplary embodiment of the present disclosure, the blocking layer may include an oxygen permeation blocking layer.

In another general aspect, a packaging material includes the polyethylene multilayer structure film according to an exemplary embodiment of the present disclosure.

In still another general aspect, a molded article includes the packaging material according to an exemplary embodiment of the present disclosure.

According to an exemplary embodiment of the present disclosure, the molded article may be any one selected from a powder detergent package, a powder product packaging film, a liquid product packaging film, an ice pack, a frozen food packaging bag, a frozen food container, a refrigerated food packaging bag, a refrigerated food container, a shrink film, a heavy packaging film, an automatic packaging film, a stretch wrap, and a bag.

According to an exemplary embodiment of the present disclosure, the molded article may be selected according to the request of printing on the rear side of the printed layer in the distribution/sales process during packaging of liquid/powder/solid contents.

Since the packaging material including the polyethylene multilayer structure film according to the present disclosure is manufactured from a film composed of a single polyethylene material and is recyclable, it has an effect of not causing environmental pollution.

In addition, the packaging material including the polyethylene multilayer structure film according to the present disclosure has mechanical properties and thermal properties which are not greatly deteriorated as compared with a conventional laminated film of different materials and a packaging material manufactured therefrom, and thus, may minimize damage in the process of printing and commercialization.

Since the packaging material including the polyethylene multilayer structure film according to the present disclosure maintains a difference in melting point between resin components forming the printed layer (A) and the heat sealing layer (B) of 20°C or more, thermal adhesion may be performed in a low temperature range, and a thermal adhesion speed may be increased.

Hereinafter, the polyethylene multilayer structure film according to the present disclosure, and a packaging material manufactured using the same will be described in detail.

Herein, unless otherwise defined, all technical terms and scientific terms have the same meanings as those commonly understood by one of those skilled in the art to which the present disclosure pertains. The terms used herein are only for effectively describing a certain specific example, and are not intended to limit the present disclosure.

Further, the unit of added materials which is not particularly described in the specification may be wt%.

In addition, the singular form used in the specification and claims appended thereto may be intended to also include a plural form, unless otherwise indicated in the context.

Hereinafter, unless otherwise particularly defined in the present specification, the term "polymer" may refer to a polymerizable compound prepared by polymerizing a monomer. Specifically, the polymer may include a homopolymer, a copolymer, a terpolymer, an interpolymer, and the like. The "interpolymer" refers to a polymer prepared by polymerizing two or more monomers different from each other. Therefore, the generic term "interpolymer" may include a terpolymer as well as a copolymer. The copolymer refers to a polymer prepared from two different monomers, and the terpolymer refers to a polymer prepared from three different monomers.

Hereinafter, unless otherwise particularly defined in the present specification, it will be understood that when it is described that a part such as a layer, a film, a thin film, a region, or a plate is "on" or "above" another part, it may include not only the case of being "directly on" the other part but also the case of intervening another part therebetween.

"Openability" described in the present disclosure generally means opening a sealed by release, and "easy tear" also means being easily torn when using a product such as a coffee mix and has the meaning included in the openability described above.

In addition, "and/or" of the present disclosure refers to inclusion each of the mentioned items and all combinations of one or more thereof.

Since the present disclosure uses a polyethylene single material, a polyethylene multilayer structure film which is recyclable so that it does not cause environmental pollution, does not have mechanical properties and thermal properties which are not greatly deteriorated as compared with a conventional laminated film of different materials and a packaging material manufactured therefrom, so that it may minimize damage in the process of print processability and commercialization, and has a constant printing focus so that printed contents may be clearly identified, and a packaging material using the same may be provided.

Hereinafter, the present disclosure will be described in more detail.

The present disclosure provides a polyethylene multilayer structure film including: a printed layer (A) and a heat sealing layer (B),

wherein the printed layer (A) has a monolayer or multilayer structure including a layer including a mixed resin including any one polyethylene resin selected from a linear low-density polyethylene resin (LLDPE), a metallocene linear low-density polyethylene resin (mLLDPE), and a low-density polyethylene resin (LDPE) and a high-density polyethylene resin (HDPE), when the printed layer A is a single layer, the high-density polyethylene resin (HDPE) is included at 50 wt% to 95 wt% and when the printed layer A is multi-layered, a structure of an outermost layer (A1) and an intermediate layer (A2) is included, in which the outermost layer (A1) includes 50 wt% or more of the high-density polyethylene resin (HPDE) and at least one layer of the intermediate layer (A2) includes 90 wt% or less of the high-density polyethylene resin (HDPE),

the heat sealing layer (B) includes an upper layer (B1), a middle layer (B2), and an adhesive layer (B3), the upper layer (B1) and the middle layer (B2) include any one or more polyethylene resins selected from a linear low-density polyethylene resin (LLDPE), a metallocene linear low-density polyethylene resin (m-LLDPE), a medium-density polyethylene resin (MDPE), and a high-density polyethylene resin (HDPE), the adhesive layer (B3) includes a polyolefin elastomer and/or a polyolefin plastomer, and

a difference in melting temperature between the adhesive layer (B3) of the heat sealing layer (B) and the single layer of the printed layer (A) or the outermost layer (A1) of the printed layer (A) when the printed layer is multi-layered satisfies the following Equation 1:

[Equation 1]

In addition, according to an exemplary embodiment of the present disclosure, an MD elongation ratio in accordance with ASTM D 638 between the printed layer (A) and the heat sealing layer (B) may satisfy the following Equation 2, and a TD elongation ratio may satisfy the following Equation 3:

[Equation 2]

[Equation 3]

Since the MD elongation ratio in accordance with ASTM D 638 of the printed layer (A) and the heat sealing layer (B) satisfies Equations 2 and 3, the durability of the polyethylene multilayer structure film is excellent, and processability is also excellent.

The polyethylene multilayer structure film is manufactured from a film composed of a polyethylene single material, so that it is recyclable and may have mechanical strength similar to that when using different polymer resins such as PET and nylon.

In addition, in the present disclosure, the printed layer (A) may not be stretched. As the polyethylene multilayer structure film includes the unstretched printed layer (A), printability may be very improved due to the low shrinkage rate of the printed layer (A).

The shrinkage rate of the printed layer (A) according to the present disclosure may be 30% or less in MD under the conditions of 0.02 N and 128°C and 20% or less in MD under the conditions of 0.05 N and 128°C, specifically, 25% or less in MD under the conditions of 0.02 N and 128°C and 10% or less in MD under the conditions of 0.05 N and 128°C, and specifically, 20% or less in MD under the conditions of 0.02 N and 128°C and 7% or less in MD under the conditions of 0.05 N and 128°C, but is not limited thereto.

Since the shrinkage rate satisfies the conditions under the temperature conditions and tension, printability is excellent and the durability of the film is also excellent, and thus, when it is printed on the surface of the polyethylene multilayer structure film, print quality is excellent and the print quality at a low temperature may be maintained.

The high-density polyethylene (HDPE) resin included in the printed layer (A) may have a density of 0.935 to 0.97 g/cm³, specifically 0.950 to 0.968 g/cm³, and specifically 0.955 to 0.965 g/cm³, but is not necessarily limited thereto. In addition, the high-density polyethylene resin (HDPE) may have a melt index of 0.1 to 10 g/10 min, specifically 0.2 to 10 g/10 min, when measured under a load of 2.16 kg at 190°C in accordance with ASTM D1238 D, and also, the high-density polyethylene resin (HDPE) may have a weight average molecular weight (Mw) of 100,000 to 1,000,000 g/mol, specifically 200,000 to 900,000 g/mol, and specifically 100,000 to 800,000 g/mol, but is not limited thereto.

In addition, the low-density polyethylene resin (LDPE) included in the printed layer (A) may have a density of 0.918 to 0.925 g/cm³, and may have a melt index of 0.2 to 20 g/10 min, specifically 0.2 to 10 g/10 min, and specifically 0.2 to 7 g/10 min, when measured under a load of 2.16 kg at 190°C in accordance with ASTM D1238 D, but is not limited thereto.

In addition, the metallocene linear low-density polyethylene resin (mLLDPE) included in the printed layer (A) may have a density of 0.910 to 0.940 g/cm³, and a melt index of 0.2 to 20 g/10 min, specifically 0.2 to 10 g/10 min, specifically 0.2 to 5 g/10 min, and specifically 1 to 3 g/10 min, when measured under a load of 2.16 kg at 190°C in accordance with ASTM D1238 D, but is not limited thereto.

The printed layer (A) may be composed of a single layer, two layers or more, and specifically three layers or more.

When the printed layer (A) is a single layer, the high-density polyethylene resin (HDPE) may be included at 20 wt% to 90 wt%, specifically 30 wt% to 90 wt%, and specifically 50 wt% to 90 wt%, but is not limited thereto.

When the printed layer (A) is two or more layers, it may be composed of an outermost layer (A1) and an intermediate layer (A2), and the outermost layer (A1) includes 50 wt% or more of the high-density polyethylene resin (HDPE) and at least one layer of the intermediate layer may include 90 wt% or less of the high-density polyethylene resin (HDPE).

When the printed layer (A) is three layers or more, the three layers may be formed of an outermost layer (A1) provided on the uppermost, an intermediate layer (A2) provided under the outermost layer (A1), and a lower layer (A3) provided under the intermediate layer (A2). A mixing ratio of any one polyethylene resin selected from a linear low-density polyethylene resin (LLDPE), a metallocene linear low-density polyethylene resin (mLLDPE), and a low-density polyethylene resin (LDPE) and a high-density polyethylene resin (HDPE) forming the outermost layer (A1), the intermediate layer (A2), and the lower layer (A3) is adjusted, whereby a density relationship of the outermost layer (A1), the intermediate layer (A2), and the lower layer (A3) may be expressed by the following Equation 4:

[Equation 4]

wherein the density was measured in accordance with ASTM D 792, the unit of the density is g/cm³, M1 is a density of the outermost layer (A1), and M2 is a density of the intermediate layer (A2).

In addition, the lower layer (A3) may use 0 to 50 wt% of the low density polyethylene resin (LDPE) or the metallocene linear low-density polyethylene resin/medium-density polyethylene resin ((m)LLDPE/MDPE) when 100 wt% or less of the high-density polyethylene resin (HDPE) is used.

By satisfying the density ratio, the mechanical strength of the printed layer (A) may be similar to that of the conventional resin such as nylon or PET, and the printed layer is flexible and has good rigidity. Besides, since printing focus is maintained, visibility of printed contents becomes better.

In addition, according to an exemplary embodiment of the present disclosure, the melting temperature of the single layer of the printed layer (A) or the outermost layer (A1) of the multiple layers of the printed layer (A) may be 127°C or higher, and the melting temperature of the adhesive layer (B3) of the heat sealing layer (B) may be 108°C or lower. As the melting temperature is satisfied, extrusion molding is easy.

In addition, the printed layer (A) including one or more layers may have a film thickness of 60 μm or less, specifically 10 to 60 μm, and specifically 20 to 60 μm, but is not limited thereto. Since the printed layer (A) having the thickness may have excellent mechanical strength with low tear strength, a polyethylene multilayer structure packaging material having excellent flexibility may be provided. In particular, the polyethylene multilayer structure packaging material is appropriate for use in a product requiring easy tear due to its low tear strength.

The printed layer (A) may have a haze of 25% or less, specifically 10 to 20%, and specifically 10 to 15%, but is not limited thereto. When the haze value is satisfied, the polyethylene multilayer structure film has good transparency and a constant print focus.

The elastic modulus of the printed layer (A) was measured by a 1% secant modulus method, and the elastic modulus value may be 4,000 kg/cm² or more in MD and 4,000 kg/cm² or more in TD, specifically 4,000 to 8,000 kg/cm² in MD and 6,000 to 10,000 kg/cm² in TD. As the printed layer (A) satisfies the 1% secant modulus values in MD or TD in the above range, film dimensional stability in printing operation is increased and a polyethylene multilayer structure packaging material having excellent printability may be provided.

In addition, the printed layer (A) may have a tear strength value of 60.0 g/μm or less in TD and 1.0 g/μm in MD, specifically 30 to 60.0 g/μm in TD and 0.01 to 1.0 g/μm in MD, and by satisfying the range, it has excellent openability and better tensile strength and elongation at break. In particular, as the polyethylene multilayer structure packaging material has the tear strength value, consumers may easily open the packaging by hand.

In the polyethylene multilayer structure film, the heat sealing layer (B) includes an upper layer (B1) including any one or more polyethylene resins selected from a linear low-density polyethylene resin (LLDPE) and a metallocene linear low-density polyethylene resin (m-LLDPE) and a high-density polyethylene resin (HDPE), an middle layer (B2) including a linear low-density polyethylene resin (LLDPE) and/or a metallocene linear low-density polyethylene resin (m-LLDPE), and an adhesive layer (B3) including a polyolefin elastomer and/or a polyolefin plastomer, and the resin forming the adhesive layer (B3) is a polyethylene-based resin having a melting point lower than the melting point of the mixed resin forming the printed layer (A) by 20°C or more. More specifically, the resin forming the adhesive layer (B3) of the heat sealing layer (B) may be a polyethylene-based resin having a melting point lower than the melting point of the resin forming the outermost layer (A1) of the printed layer (A) by 20°C or more. In terms of the thermal adhesiveness at low temperature of the packaging material, the difference in melting point is preferably 20 to 90°C. When the difference in melting point satisfies 20 to 90°C, both the durability of a film surface area in a low temperature state and burst strength in a thermal adhesion boundary area show excellent values, and the utilization value in various temperature ranges including a low temperature is very high. When the difference in melting point is satisfied, a heat sealing process at a sufficiently low temperature may proceed, the physical properties of the laminated film are not deteriorated, and excellent heat sealability and high-speed bag making processability of a film may be implemented.

In particular, when a high-speed bag making processability is deteriorated, this leads to the price increase of the produced packaging material, and thus, the productivity and the economic feasibility of the film and the packaging material are greatly reduced, and the polyethylene multilayer structure film of the present disclosure may have improved bag making processability of the film and obtain an economic effect therefrom.

The adhesive layer (B3) of the heat sealing layer (B) may include a polyethylene-based resin having a melting point of 108°C or lower, specifically 60 to 80°C, and specifically 79 to 80°C. When the melting point range is satisfied, thermal adhesion may be performed at a low thermal adhesion start temperature for thermal adhesion. The thermal adhesion start temperature may be 40 to 120°C, preferably 50 to 110°C, and more preferably 50 to 100°C, but is not limited thereto. The thermal adhesion start temperature refers to a temperature when the adhesion strength of the heat sealing layer (B) measured in accordance with ASTM F2029 and ASTM F88 is 2000 to 3000 gf based on a product in which layers of 1000 gf or more are specifically laminated. By satisfying the ranges described above of the melting point and the thermal adhesion starting temperature of the heat sealing layer (B), the polyethylene multilayer structure film according to the present disclosure and the packaging material manufactured therefrom may implement excellent effects of heat sealability and high-speed bag making processability of the film better, even in a sufficiently low temperature range where the printed layer (A) and the heat sealing layer (B) of the film are not damaged or the physical properties thereof are not deteriorated.

In addition, the adhesive layer (B3) of the heat sealing layer (B) may further include any one or more polyethylene resins selected from a low-density polyethylene resin (LDPE), a linear low-density polyethylene resin (LLDPE), a metallocene linear low-density polyethylene resin (m-LLDPE), a medium-density polyethylene resin (MDPE), and a high-density polyethylene resin (HDPE), and specifically, may further include a linear low-density polyethylene resin (LLDPE), depending on the use, but is not limited thereto.

By further including the linear low-density polyethylene resin in the adhesive layer (B3), the adhesive layer (B3) may have a melting point of 100 to 130°C, specifically 100 to 125°C, and specifically 100 to 123°C, but is not limited thereto.

In addition, the adhesive layer (B3) may further include any one or more polymer resins selected from a bimodal polyolefin plastomer, a bimodal polyolefin elastomer, a unimodal polyolefin plastomer, and a unimodal polyolefin elastomer.

A metallocene linear low-density polyethylene resin (m-LLDPE) and/or a high-density polyethylene resin (HDPE) may be included in the upper layer (B1) of the heat sealing layer (B), and the high-density polyethylene resin (HDPE) may have a density of 0.935 to 0.97 g/cm³, specifically 0.950 to 0.968 g/cm³, specifically 0.955 to 0.965 g/cm³, but is not necessarily limited thereto. In addition, the high-density polyethylene resin (HDPE) may have a melt of 0.1 to 20 g/10 min, specifically 0.1 to 10 g/10 min, and specifically 0.2 to 10 g/10 min, when measured under a load of 2.16 kg at 190°C in accordance with ASTM D 1238.

In addition, the high-density polyethylene resin (HDPE) may have a weight average molecular weight (Mw) of 100,000 to 1,000,000 g/mol, specifically 200,000 to 900,000 g/mol, and specifically 100,000 to 800,000 g/mol, but is not limited thereto.

The metallocene linear low-density polyethylene resin (m-LLDPE) may be a linear low-density polyethylene resin prepared from monomers including a comonomer using a metallocene catalyst, and the metallocene linear low-density polyethylene resin (m-LLDPE) may have a density of 0.868 to 0.935 g/cm³, specifically 0.90 to 0.920 g/cm³, specifically 0.910 to 0.920 g/cm³, and specifically 0.916 to 0.920 g/cm³, but is not necessarily limited thereto. In addition, the metallocene linear low-density polyethylene resin (m-LLDPE) may have a melting temperature of 130°C or lower, specifically 110 to 125°C, a number average molecular weight of 39,000 to 54,000 g/mol, specifically 45,000 to 54,000 g/mol, a weight average molecular weight of 50,000 to 200,000 g/mol, specifically 90,000 and 150,000 g/mol, and a polydispersity index (PDI) of 2.0 to 3.5, specifically 2.0 to 3.0. When the density range is satisfied, transparency and strength are excellent, and mixability with polyethylene-based resins is good.

A metallocene linear low-density polyethylene resin (m-LLDPE) and a high-density polyethylene resin (HDPE) may be included in the upper layer (B1) of the heat sealing layer (B), the metallocene linear low-density polyethylene resin (m-LLDPE) and the high-density polyethylene resin (HDPE) may be mixed at 10 to 90 wt%, respectively, and by mixing at the content ratio, the transparency, the tear strength, and the stabbing strength of the polyethylene multilayer structure film may be improved.

A metallocene linear low-density polyethylene resin (m-LLDPE) may be included in the middle layer (B2) of the heat sealing layer (B), and specifically, a mixed resin of the metallocene linear low-density polyethylene resin (m-LLDPE) and a polyolefin plastomer (POP) may be included. When the mixed resin of the metallocene linear low-density polyethylene resin (m-LLDPE) and the polyolefin plastomer (POP) are included, the metallocene linear low-density polyethylene resin (m-LLDPE) may have a density of 0.912 to 0.920 g/cm³ considering the mixability with the polyolefin plastomer (POP). By mixing two polymer resins having the above properties, the polyethylene multilayer structure film may be sealed even at a low temperature and may have a wider available temperature range for sealing.

The packaging material manufactured of the polyethylene multilayer structure film according to the present disclosure has excellent humidity barrier properties, may prevent contamination by particulate contaminants, and has improved stabbing strength to have a wider use range of the packaging material.

The mixing of the metallocene linear low-density polyethylene resin (m-LLDPE) and the polyolefin plastomer (POP) according to the present disclosure may be determined as a mixing ratio until a hot tack strength ratio in accordance with ASTM F1921 of the adhesive layer (B3) of the heat sealing layer (B) and the middle layer (B2) including the metallocene linear low-density polyethylene resin (m-LLDPE) and the polyolefin plastomer (POP) is 0.7 to 1.0 (B3/B2) and a heat sealing strength ratio at 90°C of the adhesive layer (B3) and the middle layer (B2) is 0.6 to 1.0 (B3/B2).

Specifically, the metallocene linear low-density polyethylene resin (m-LLDPE) is mixed with the polyolefin plastomer (POP) so that the content of m-LLDPE is up to 80 wt%. The properties of the polyolefin plastomer (POP) are the same as the polyolefin plastomer (POP) included in the adhesive layer (B3) of the heat sealing layer (B).

In addition, the adhesive layer (B3) of the heat sealing layer (B) may include a polyethylene-based resin having a melting point of 60 to 108°C, specifically a polyethylene-based resin having a melting point of 80 to 108°C. When the melting point is satisfied, the polyethylene multilayer structure film according to the present disclosure may be laminated even at a low temperature. The polyethylene-based resin may be a polyolefin elastomer resin or a polyolefin plastomer (POP) resin, and the polyolefin plastomer may have a density of 0.885 to 0.910 g/cm³, or 0.869 to 0.902 g/cm³.

The upper layer (B1), the middle layer (B2) and the adhesive layer (B3) forming the heat sealing layer (B) are characterized in that a hot tack strength ratio in accordance with ASTM F1921 has relationship represented by Equation 5:

[Equation 5]

1 ≤ (HTS₁/HTS₂)<(HTS₃/HTS₂)

wherein HTS₁ is a hot sealing strength value of the upper layer B1, HTS₂ is a hot sealing strength value of the middle layer (B2), and HTS₃ is a hot sealing strength value of the adhesive layer (B3). The hot sealing strength value is measured at 100°C.

The tear strength of the heat sealing layer (B) may be 30.0 g/μm or less in TD and 20.0 g/μm or less in MD.

In the heat sealing layer (B), a thickness ratio of the upper layer (B1), the middle layer (B2), and the adhesive layer (B3) may be 1:1 to 10:0.2 to 2, specifically, 1:1 to 8: 0.2 to 1, and specifically 1:4 to 8:0.2 to 1, but is not necessarily limited thereto.

When the thickness of each layer satisfies the ratio of the above range, a characteristic in which falling ball impact strength and stabbing strength per unit thickness are excellent in balance may be implemented better, and durability at a low temperature may be further improved.

According to an exemplary embodiment of the present disclosure, in the puncture test in accordance with ASTM D4830, the printed layer (A) may be 30 N or more and the heat sealing layer (B) may be 80 N or more, and specifically, the printed layer (A) may be 30 to 50 N, specifically 30 to 40 N and the heat sealing layer (B) may be 80 to 100 N, specifically 90 to 100 N, but is not limited thereto.

The printed layer (A) according to an exemplary embodiment of the present disclosure may have a tensile strength of 500 kgf/cm² or more in MD and 300 kgf/cm² or more in TD, and specifically, 500 to 800 kgf/cm² or more in MD and 300 to 600 kgf/cm² or more in TD, in accordance with ASTM D 892, but is not limited thereto.

In addition, the heat sealing layer (B) may have a tensile strength of 300 kgf/cm² or more in MD and 300 kgf/cm² or more in TD, specifically, 300 to 600 kgf/cm² and 300 to 700 kgf/cm² in TD, but is not limited thereto.

In addition, the polyethylene multilayer structure film according to the present disclosure may have a tensile strength of 150 kgf/cm² or more, specifically 200 kgf/cm² or more, and specifically 200 to 400 kgf/cm² in MD and 200 kgf/cm² or more, specifically 300 kgf/cm² or more, and specifically 300 to 500 kgf/cm² in TD, but is not limited thereto. In addition, the tensile strength satisfies the range, the polyethylene multilayer structure film according to the present disclosure has better mechanical properties and the damage of the film may be further minimized in the process of commercialization.

The printed layer (A) according to an exemplary embodiment of the present disclosure may have an elongation of 300% or more in MD and 800% or more in TD, specifically 300 to 500% in MD and 800 to 1,000% in TD, in accordance with ASTM D 638, but is not limited thereto.

In addition, the heat sealing layer (B) may have an elongation of 400% or more in MD and 500% or more in TD, specifically 400 to 800% in MD and 500 to 900% in TD, in accordance with ASTM D 638, but is not limited thereto.

The heat sealing layer (B) according to an exemplary embodiment may have a film thickness of 250 μm or less, or 30 to 250 μm, but is not limited thereto.

The polyethylene multilayer structure film according to the present disclosure may have a total thickness of 300 μm or less, specifically 250 μm or less, and specifically 100 to 250 μm, but is not limited thereto. By satisfying the range of the total thickness, the polyethylene multilayer structure film of the present disclosure may have further improved durability.

The polyethylene multilayer structure film according to the present disclosure may have a falling ball impact strength of 2.0 to 13.0 g/μm, specifically 3.0 to 13.0 g/μm, and specifically 3 to 8.0 g/μm, but is not limited thereto. In addition, a stabbing strength per unit thickness may be 0.25 to 1.5 N/μm, specifically 0.50 to 1.4 N/μm, and specifically 0.90 to 1.3 N/μm, but is not limited thereto.

The falling ball impact strength refers to a value measured in accordance with ASTM D 1709, the stabbing strength refers to a value obtained by measuring a maximum strength when a film is stabbed with a pin having a diameter of 19.05 mm sticks in the inner direction of the film at a speed of 250 mm/min to be torn, and the falling ball impact strength and the stabbing strength per unit thickness refer to numerical values obtained by the falling ball impact strength and stabbing strength values measured as described above by the total thickness of the film.

The linear low-density polyethylene resin (LLDPE) and the metallocene linear low-density polyethylene resin (m-LLDPE) used in the present disclosure may be an ethylene copolymer in which ethylene and C3-C18 α-olefin comonomer are polymerized.

Specifically, the α-olefin comonomer may be any one or a mixture of two or more selected from propylene, 10-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene, and specifically, the α-olefin comonomer may be any one or a mixture of two or more selected from 1-propylene, 1-butene, 1-hexene, 1-heptene, and 1-octene, but is not limited thereto.

By using the α-olefin comonomer described above, a high molecular weight ethylene copolymer may be prepared while imparting flowability to an ethylene homopolymer, and thus, the polyethylene multilayer structure film including the copolymer may have further improved mechanical properties such as impact resistance and tensile strength.

The content of the α-olefin comonomer included in 100 parts by weight of the ethylene copolymer may be 1 to 40 parts by weight, specifically 1 to 30 parts by weight, and specifically 1 to 20 parts by weight, but is not limited thereto.

The polymer used in the present disclosure may be obtained by appropriately selecting a polymerization method. For example, single polymerization by any one selected from gas phase polymerization, slurry polymerization, solution polymerization, high pressure ion polymerization, and the like using a multi-site catalyst such as a Ziegler-Natta catalyst or a single site catalyst such as a metallocene-based catalyst or multistage polymerization by a combination thereof may be performed, but this is only a non-limiting example, and the present disclosure is not necessarily limited thereto.

The single site catalyst is a catalyst capable of forming a uniform active species, and is generally obtained by bringing any one compound selected from metallocene-based transition metal compounds and non-metallocene-based transition metal compounds and a cocatalyst for activation into contact.

Here, since the single site catalyst has a homogeneous active site structure as compared with a multi-site catalyst, it may polymerize a polymer having high molecular weight and high uniformity structure, and thus, polymerization using a single site catalyst is preferred, and among the single site catalysts, polymerization using a metallocene-based catalyst is more preferred, but is not necessarily limited thereto.

A method of manufacturing a polyethylene multilayer structure film according to the present disclosure using the ethylene polymer or the ethylene copolymer used in the present disclosure is not limited as long as it may derive the effect to be obtained in the present disclosure. For example, an injection molding method, an extrusion molding method, an inflation method, a T-die method, a calender method, a blow molding method, a vacuum molding method, a dry lamination method, an air pressure molding method, and the like may be used, and a dry lamination method is more preferred in deriving the effect according to the present disclosure, but is only a non-limiting example, and is not necessarily limited thereto.

Here, the polyethylene multilayer structure according to the present disclosure may be implemented even by lamination once or twice or more, and also implemented by coextrusion using a plurality of extruders, but is not necessarily limited thereto. Here, in the case of coextrusion, the number of extruders is adjusted, thereby implementing various physical properties of the film better.

The polyethylene multilayer structure film according to the present disclosure may further include one or more layers between the outermost layer (A1) and the lower layer (A3) of the printed layer (A).

Here, the blocking layer may include any one or two or more layers selected from a barrier coating layer, a top coating layer, a printing layer, and the like, and more specifically, may include an aluminum deposition layer, an oxygen blocking layer, an impact resistance reinforcement layer, a thermal resistance reinforcement layer, and the like, and specifically, the oxygen blocking layer may be ethylene vinyl alcohol (EVOH) and the like and the impact resistance reinforcement layer may be polyamide (PA), polyester, and the like, but is not necessarily limited thereto.

Another exemplary embodiment of the present disclosure provides a packaging material manufactured from the polyethylene multilayer structure film described above and a molded article including the same. Here, the molded article is not limited thereto as long as it is selected according to the request of a print on the rear surface of the printed layer in the process of distribution/sales during packaging of liquid/powder/solid contents, and specifically, may include a powder detergent package, a powder product packaging film, a liquid product packaging film, an ice pack, a frozen food packaging bag, a frozen food container, a refrigerated food packaging bag, a refrigerated food container, a shrink film, a heavy packaging film, an automatic packaging film, a stretch wrap, a bag, and the like.

The packaging material according to an exemplary embodiment of the present disclosure may maintain excellent durability and mechanical properties in a wide temperature range including a low temperature, in spite of continuous temperature change in a manufacturing process at room temperature, a heat sealing process at a high temperature, and distribution and storage process at low temperature, and the like. Therefore, it is more preferred that the packaging material is applied to the molded article utilized at a low temperature such as an ice pack, a frozen food packaging bag, and a frozen food container, considering the effect according to the present disclosure, but this is only a non-limiting example, and is not necessarily limited thereto.

Hereinafter, the present disclosure will be described in more detail with reference to the Examples and Comparative Examples. However, the following examples and comparative examples are only an example for describing the present disclosure in more detail, and do not limit the present disclosure in any way.

[Method of measuring physical properties]

(1) Density

Measurement was performed in accordance with ASTM D 792.

(2) Melt index

Measurement was performed at 190°C under 2.16 kg in accordance with ASTM D 1238.

(3) Haze

The haze was measured in accordance with ASTM D 1003.

(4) Falling ball impact strength

Measurement was performed in accordance with ASTM D 1709.

(5) Hot tack strength

Hot tack strength was measured in accordance with ASTM F1921.

(6) Stabbing strength

A maximum strength when a film was stabbed with a pin having a diameter of 6.5 mm at a speed of 500 mm/min in the inner direction to be torn was measured.

(7) Elastic modulus

The elastic modulus was measured by a 1% secant modulus method, and specifically was measured in accordance with ASTM D882 in the machine direction (MD) and the transverse direction (TD).

(8) Tensile strength

Measurement was performed in accordance with ASTM D 892. The unit of the tensile strength was kg/cm².

(9) Tear strength

The tear strength was measured in accordance with KS M ISO 1974 with a measuring instrument of the Elmendorf style (Toyoseiki).

(10) Heat adhesiveness

Thermal adhesion strength was measured in accordance with ASTM F2029 and ASTM F88. A thermal adhesion start temperature was based on adhesive strength of 1000 kgf or more.

(12) Low temperature burst strength in a thermal adhesion boundary area

As a durability scale in a thermal adhesion area of a packaging material at a low temperature, impact was applied to the thermally adhered area at a low temperature to evaluate a total energy value required when the corresponding area was torn. Both inner surfaces of the film were overlapped and thermally adhered at 0.2 MPa for 1 second with a heating bar at 125°C, and then a weight of 5.381 kg having a diameter of 20 mm was dropped at a speed of 4.3 kg/ms to the thermally adhered boundary area of the film stored for 1 hour or more, thereby measuring an energy value required when the thermally adhered boundary area of the film was torn.

(13) Evaluation of packaging drop at room temperature

As the durability scale of the packaging material at room temperature, a damage degree according to the packaging material drop at room temperature was evaluated. A sample obtained by filling a packaging material specimen manufactured from a film filled with 3.5 kg of powder (detergent) and sealing three sides was manufactured (180 mm Х 340 mm), and the manufactured sample was dropped from a height of 1.5 m to determine whether the damage degree was confirmed, thereby evaluating the durability as the evaluation criterion of the following Table 1.

Classification	◎(Excellent)	○(Good)	×(Poor)
Sample damage degree	All 10 samples were not damaged and no powder inside was released.	No scratch in appearance was observed and powder inside was not released in some products.	It was observed that one or more of the samples were burst or torn and powder was released.

(14) Bag making speedThe bag making speed is a scale of productivity of making a bag by a thermal adhesion processing, and shows the number of production per minute to be reached when the thermal adhesion conditions were optimized. In the examples of the present disclosure, it was measured that 25 or more per minute were produced on average.

(15) Measurement of shrinkage rate

Thermomechanical analysis (TMA) equipment was used for the film, and the measurement method was in accordance with ASTM E831.

[Manufacture of printed layer (A) film]

[Manufacturing Example A-1]

As the outermost layer (A1) included in the printed layer (A) including three plural layers, YUZEX 8300 (density: 0.963 g/cm³, melting point: 133°C, melt index: 0.7 g/10 min (190°C, 2.16 kg)) available from SKGC which was a high-density polyethylene resin (HDPE) was used, as the intermediate layer (A2), SKGC YUCLAIR FN800M (density: 0.935 g/cm³, melting point: 129°C, melting index: 1.0 g/10 min (190°C, 2.16 kg) which was a high-density polyethylene resin (HDPE) was used, and as the inner layer (A3), YUZEX 8300 (density: 0.963 g/cm³, melting point: 133°C, melting index: 0.7 g/10 min (190°C, 2.16 kg)) available from SKGC which was a high-density polyethylene resin (HDPE) was used. In all of the outermost layer, the middle layer, and the inner layer, about 10 wt% of a low-density polyethylene resin (LDPE) (BS500 available from LG (density: 0.921 g/cm³, melting point: 109°C, melt index: 3.3 g/10 min (190°C, 2.16 kg))) was mixed therewith.

The resin was coextruded by blown film molding while adjusting a processing temperature for each layer from 165°C to 195°C using a total of three extruders having a screw size of 24 pi for film lamination, thereby forming the printed layer (A) having a multilayer structure.

At this time, a die diameter was 300 mm, a die gap was 3.5 mm, a bubble expansion ratio during film manufacture was 2.1 or less, and a cooling line cooled by air had a height of 12 cm based on a die. The cooled and solidified film was pulled by a nip roller and wound into a film roll. As the film in each layer, an unstretched film was used, and the thickness and the total thickness of each layer of the film were 9 μm/11 μm/5 μm (total 25 μm).

The physical properties of the thus-obtained printed layer(A) are shown in the following Table 2.

[Manufacturing Example A-2]

In all of the outermost layer (A1), the intermediate layer (A2), and the inner layer (A3) included in the printed layer (A) including three plural layers, 90 wt% of YUZEX 8300 available from SKGC (density: 0.963 g/cm³, melting point: 133°C, melt index: 0.7 g/10 min (190°C, 2.16 kg)) as a high-density polyethylene resin (HDPE) and 10 wt% of BS500 (density: 0.921 g/cm³, melting point: 109°C, melt index: 3.3 g/10 min (190°C, 2.16 kg)) as a low-density polyethylene resin (LDPE) were mixed and applied to each layer.

At this time, a die diameter was 300 mm, a die gap was 3.5 mm, a bubble expansion ratio during film manufacture was 2.1 or less, and a cooling line cooled by air had a height of 12 cm based on a die. The cooled and solidified film was pulled by a nip roller and wound into a film roll. As the film in each layer, an unstretched film was used, and the thickness and the total thickness of each layer of the film were 7.5 μm/15 μm/7.5 μm (total 30 μm).

[Manufacture of heat sealing layer (B) film]

[Manufacturing Example B-1]

As the upper layer (B1) of the heat sealing layer (B), a SK Smart 151 (S) product which was a metallocene linear low-density polyethylene resin (density: 0.915 g/cm³, melt index: 1.0 g/10 min (190°C, 2.16 kg), melting temperature: 115°C, dispersion index (PDI): 2.25) was used.

As the middle layer (B2) of the heat sealing layer (B), a SK Smart 181 (S) product which was a metallocene linear low-density polyethylene resin (density: 0.918 g/cm³, melt index: 1.0 g/10 min (190°C, 2.16 kg), melting temperature: 118°C, dispersion index (PDI): 2.25) was used. In addition, as the adhesive layer (B3) of the heat sealing layer (B), a SK Supreme 891 product which was a polyolefin plastomer resin (density: 0.885 g/cm³, melt index: 1.0 g/10 min (190°C, 2.16 kg), melting temperature: 79°C, dispersion index (PDI): 2.8) was used.

At this time, the resin was coextruded by blown film molding with adjustment of the processing temperature for each layer from 165°C to 195°C using a total of three extruders having a screw size of 24 pi while filtering the resin so that the resin did not pass, thereby forming a heat sealing layer (B) film having a multilayer structure of three layers.

At this time, a die diameter was 300 mm, a die gap was 4 mm, and an expansion ratio of bubble in film manufacture was 2.1 or less, and the cooling line cooled by air had a height of 12 cm based on the die. The thickness of each layer and the total thickness of the film was 35.06 μm/39.85 μm/15.71 μm (total thickness: 90 μm). The heat sealing layer (B) had a tear strength in MD of 14.1 g/μm, a tear strength in TD of 28.3 g/μm, and a sealing start temperature of 90°C. The physical properties of the thus-obtained printed layer(A) are shown in the following Table 2.

[Example 1]

The printed layer (A) of Manufacturing Example A-1 and the heat sealing layer (B) manufactured above were laminated to manufacture a polyethylene multilayer structure film packaging material. The lower layer (A3) of the printed layer (A) film and the upper layer (B1) of the heat sealing layer (B) were laminated, put into a dry lamination machine, and adhered to manufacture a polyethylene multilayer structure film packaging material.

The physical properties of the polyethylene multilayer structure film packaging material are shown in the following Table 2.

[Comparative Example 1]

A polyethylene multilayer structure film was manufactured in the same manner as in Example 1, except that the printed layer (A) film was composed of only nylon (25 μm, NY film, JK Materials), not a three-layer structure.

The physical properties of the thus-obtained polyethylene multilayer structure film are shown in the following Table 2.

	Puncture (N)	Haze (%)	Tensile strength at break (kgf/cm²)		Elongation (%)		1% Elastic modulus (Kgf/cm²)		Tear strength (g/um)		Packaging drop effect at room temperature
	Puncture (N)	Haze (%)	MD	TD	MD	TD	MD	TD	MD	TD	Packaging drop effect at room temperature
A-1	39	13.7	697	503	383	943	7275	9961	0.5	58.6	-
A-2	31	23.9	646	341	369	899	6520	9218	0.4	57.2
B-1	92.5	-	394	440	621	752	1840	2096	14.1	28.3	-
Example 1	95.8	-	301	416	435	595	2777	2741	8.4	14.3	◎
Comparative Example 1	75.1	-	332	321	351	670	2904	3505	3.7	8.8	Х

In Example 1, an MD shrinkage rate was measured at 5.3% under the conditions of 0.05 N and 128°C, and was measured at 17.71% under the conditions of 0.02 N and 128°C. In Comparative Example 1, an MD shrinkage rate was measured at 10% under the conditions of 0.05 N and 128°C, and was measured at 23% under the conditions of 0.02 N and 128°C.Hereinabove, although the present disclosure has been described by the specific matters and limited exemplary embodiments in the present disclosure, they have been provided only for assisting the entire understanding of the present disclosure, and the present disclosure is not limited to the exemplary embodiments, and various modifications and changes may be made by those skilled in the art to which the present disclosure pertains from the description.

Therefore the spirit of the present disclosure should not be limited to the above-described exemplary embodiments, and the following claims as well as all modified equally or equivalently to the claims are intended to fall within the scope and spirit of the disclosure.

Claims

A polyethylene multilayer structure film comprising: a printed layer (A) and a heat sealing layer (B),

wherein the printed layer (A) has a monolayer or multilayer structure including a layer including a mixed resin including any one or more polyethylene resins selected from a linear low-density polyethylene resin (LLDPE), a metallocene linear low-density polyethylene resin (mLLDPE), and a low-density polyethylene resin (LDPE) and a high-density polyethylene resin (HDPE),

when the printed layer (A) is a single layer, the high-density polyethylene resin is included at 50 wt% to 95 wt% and

when the printed layer (A) is multi-layered, a structure of an outermost layer (A1) and an intermediate layer (A2) is included, in which the outermost layer (A1) includes 50 wt% or more of the high-density polyethylene resin and at least one layer of the intermediate layer (A2) includes 90 wt% or less of the high-density polyethylene resin,

the heat sealing layer (B) includes an upper layer (B1), a middle layer (B2), and an adhesive layer (B3), the upper layer (B1) and the middle layer (B2) include any one or more polyethylene resins selected from a linear low-density polyethylene resin (LLDPE), a metallocene linear low-density polyethylene resin (m-LLDPE), a medium-density polyethylene resin (MDPE), and a high-density polyethylene resin (HDPE), the adhesive layer (B3) includes a polyolefin elastomer and/or a polyolefin plastomer, and

a difference in melting temperature between the adhesive layer (B3) of the heat sealing layer (B) and the single layer of the printed layer (A) or the outermost layer (A1) of the printed layer (A) when the printed layer is multi-layered satisfies the following Equation 1:

[Equation 1]

wherein TmA is a melting temperature of the single layer of the printed layer (A) or the outermost layer (A1) of the printed layer (A) when the printed layer is multi-layered, and TmB is a melting temperature of the adhesive layer (B3) of the heat sealing layer (B).
The polyethylene multilayer structure film of claim 1, wherein an MD elongation ratio in accordance with ASTM D 638 between the printed layer (A) and the heat sealing layer (B) satisfies the following Equation 2, and a TD elongation ratio satisfies the following Equation 3:

[Equation 2]

[Equation 3]

wherein MA is an MD elongation of the printed layer (A), MB is an MD elongation of the heat sealing layer (B), TA is a TD elongation of the printed layer (A), and TB is a TD elongation of the heat sealing layer (B).
The polyethylene multilayer structure film of claim 1, wherein the printed layer is not stretched.
The polyethylene multilayer structure film of claim 3, wherein the printed layer (A) has a shrinkage rate of 30% or less in MD under the conditions of 0.02 N and 128°C and 20% or less in MD under the conditions of 0.05 N and 128°C.
The polyethylene multilayer structure film of claim 1,

wherein the high-density polyethylene resin (HDPE) included in the printed layer (A) has a density of 0.935 to 0.97 g/cm³ and a melt index of 0.2 to 10 g/10 min, and

the linear low-density polyethylene resin (LLDPE), the low-density polyethylene resin (LDPE), and the metallocene linear polyethylene resin (m-LDPE) included in the printed layer (A) have a density of 0.900 or more and less than 0.935 g/cm³ and a melt index of 0.2 to 20 g/cm³.
The polyethylene multilayer structure film of claim 1, wherein the single layer of the printed layer (A) or the outermost layer (A1) of the multiple layers of the printed layer (A) has a melting temperature of 127°C or higher and the adhesive layer (B3) of the heat sealing layer (B) has a melting temperature of 108°C or lower.
The polyethylene multilayer structure film of claim 1,

wherein the printed layer (A) has a structure of three layers or more,

the printed layer (A) includes the outermost layer (A1), the intermediate layer (A2), and a lower layer (A3), and

the lower layer (A3) is a mixed resin in which any one or more resins selected from a low-density polyethylene resin (LDPE), a linear low-density polyethylene resin (LLDPE), and a metallocene linear low-density polyethylene resin (m-LLDPE) and a high-density polyethylene resin (HDPE) are mixed.
The polyethylene multilayer structure film of claim 1, wherein the adhesive layer (B3) of the heat sealing layer (B) further includes any one or more polyethylene resins selected from a low-density polyethylene resin (LDPE), a linear low-density polyethylene resin (LLDPE), a metallocene linear low-density polyethylene resin (m-LLDPE), a medium-density polyethylene resin (MDPE), and a high-density polyethylene resin (HDPE).
The polyethylene multilayer structure film of claim 1, wherein the printed layer (A) has a haze of 25% or less, and an elastic modulus value in MD and TD of 4,000 kgf/cm² or more, as measured by a 1% secant modulus method.
The polyethylene multilayer structure film of claim 1, wherein in the heat sealing layer (B), a thickness ratio of the upper layer (B1), the middle layer (B2), and the adhesive layer (B3) is 1:1 to 10:0.2 to 2.
The polyethylene multilayer structure film of claim 1, wherein the printed layer (A) has a film thickness of 60 μm or less.
The polyethylene multilayer structure film of claim 1, wherein the heat sealing layer (B) has a film thickness of 30 to 250 μm.
The polyethylene multilayer structure film of claim 1, wherein the polyethylene multilayer structure film has a total thickness of 300 μm or less.
The polyethylene multilayer structure film of claim 1, wherein the printed layer (A) is 30 N or more and the heat sealing layer (B) is 80 N or more in a puncture test in accordance with ASTM D4830.
The polyethylene multilayer structure film of claim 1, wherein the printed layer (A) has a tensile strength of 400 kgf/cm² or more in MD and 300 kgf/cm² or more in TD, and the heat sealing layer (B) has a tensile strength of 300 kgf/cm² or more in MD and 300 kgf/cm² or more in TD, in accordance with ASTM D 892.
The polyethylene multilayer structure film of claim 1, wherein the printed layer (A) has an elongation of 300% or more in MD and 500% or more in TD, and the heat sealing layer (B) has an elongation of 400% or more in MD and 400% or more in TD, in accordance with ASTM D 638.
The polyethylene multilayer structure film of claim 1, wherein the polyethylene multilayer structure film is laminated by a dry lamination method.
The polyethylene multilayer structure film of claim 1, wherein one or more blocking layers are further included between the outermost layer (A1) and the lower layer (A3) of the printed layer (A).
The polyethylene multilayer structure film of claim 18, wherein the blocking layer includes an oxygen permeation blocking layer.
A packaging material comprising the polyethylene multilayer structure film of any one of claims 1 to 19.
A molded article comprising the packaging material of claim 20.
The molded article of claim 21, wherein the molded article is any one selected from a powder detergent package, a powder product packaging film, a liquid product packaging film, an ice pack, a frozen food packaging bag, a frozen food container, a refrigerated food packaging bag, a refrigerated food container, a shrink film, a heavy packaging film, an automatic packaging film, a stretch wrap, and a bag.
The molded article of claim 21, wherein the molded article is selected according to the request of printing on the rear side of the printed layer in a distribution/sales process during packaging of liquid/powder/solid contents.